Question

johns first three test scores out of 100 are 84,78,82. what did he score on his fourth test if the average for all four tests is 80 out of 100

Answer 1

Answer:

76

Step-by-step explanation:

Formula

$\sf Average=\dfrac{\textsf{sum of all the numbers}}{\textsf{amount of numbers}}$

Given values:

• First three test scores: 84, 78 and 82
• Total number of tests = 4
• Average score for all four tests = 80

Let x be the score of the fourth test.

To find the score of the fourth test, substitute the given values into the formula and solve for x:

$\begin{aligned} \sf Average & =\dfrac{\textsf{sum of all the numbers}}{\textsf{amount of numbers}}\\\\\implies \sf 80 & = \sf \dfrac{84+78+82+x}{4}\\\sf 80 & = \sf \dfrac{244+x}{4}\\\sf 80 \cdot 4 & = \sf 244 + x \\\sf 320 & = \sf 244 + x\\\implies \sf x & = \sf 320 - 244\\& = \sf 76\end{aligned}$

Therefore, John scored 76 on his fourth test.